In a video-on-demand (Video-on-Demand, VoD) system, one or multiple central servers generally store all video segments in which a user is interested. In addition, some local servers with limited storage capacity are deployed around a central server. Compared with the central server, these local servers are closer to the user side and may respond to a request of the user in time. When the user requests a certain video segment, the user first requests the content from a local server in the place where the user is located, (a) if the content required by the user exists on the local server, the local server directly responds to the request of the user, which is called a local hit; and
(b) if the content required by the user does not exist on the local server, the local server may guide the request of the user to another local server or the central server that stores the content, and that server provides the content for the user, which is called a local hit failure.
Since the local server has limited storage capacity, it is capable of caching only part of the video segments. When each of the local servers is configured with a poor caching policy, a large number of local hit failures may be caused. In this case, the user needs to obtain the required video segment from another local server or the central server. This may generate a large amount of network traffic, which not only increases end-to-end delay between the server and the user, but also causes network congestion. Specifically, as shown in FIG. 1, the arrows in FIG. 1 indicate flow directions of currently requested data, and the digits above the arrows indicate overlay network path labels. In FIG. 1, a user under a server 3 needs to obtain a video segment from a server 2 because of a local hit failure. In this case, traffic is generated on network paths 1 and 2 shown in FIG. 1, and therefore additional network traffic is generated. In the case of a large number of local hit failures, a large amount of network traffic may be generated.
In the prior art, the problem of an increase of the end-to-end delay between the server and the user and the network congestion occurring because a large number of local hit failures on the local server cause a large amount of network traffic is mainly solved by increasing the storage capacity of the local server, so that the local server is capable of caching more video segments, thereby implementing network capacity expansion and reducing the local hit failure ratio on the local server.
However, how to improve the local hit ratio without increasing the local server costs is a problem to be solved urgently.